Free piston well pump device



Dec. 12, 1961 D. G. KNOX FREE PISTON WELL PUMP DEVICE 3 Sheets-Sheet 1 Filed May 12, 1958 INVENTOR. K/VOA DOA/p40 6.

Dec. 12, 1961 D. G. KNOX FREE PISTON WELL PUMP DEVICE 5 Sheets-Sheet 2 Filed May 12, 1958 INVENTOR. 00114040 6. 16/1/02? BY WTOENfVS D. G. KNOX 3,012,832

FREE PISTON WELL PUMP DEVICE Dec. 12, 1961 Filed May 12, 1958 3 Sheets-Sheet 3 INVENTOR. 00/144 40 6. e/vox BY i g Filed May 12, 1958, Ser. No. 734,554 4 Claims. (Cl. 30923) This invention relates to free piston well pumping apparatus of the general type shown in my prior patents, Nos. 2,642,002 and 2,661,024, and is particularly directed to improved forms of plungers for such devices.

I have found that it is possible to produce a plunger having superior operating characteristics for some types of wells, which plunger employs one or more brush elements for sealing contact with the inner surface of the eduction tube. The brush may be formed of metallic or non-metallic bristles and these produce a sliding seal in the eduction tube. Variations in diameter and roundness of the eduction tube can therefore be tolerated to a greater extent than with conventional forms of plungers. Brush type plungers having non-metallic bristles have been found to give particularly good results in removing unwanted accumulations of water in gas wells which produce considerable quantities of sand. The brush type plunger has been found to give surprisingly good results and it is believed that the sealing effect is based upon turbulence which develops around the bristles.

In another aspect of the invention, a long plunger with spaced sealing elements is provided in order to span sections in the eduction tube which are laterally enlarged to provide space for retrieva'ble kick-off valve assemblies. Kick-oil valves are very old in the gas lift art but one of the disadvantages in their use has been the requirement that the eduction tube be pulled from the well each time it became necessary to repair or replace such valve assemblies. In more recent times, retrievable kick-off valves have been developed and are commercially available. These may be inserted and retrieved through the interior of the eduction tube on a wire line and without requiring that the eduction tube be removed from the well. Such retrievable kick-off valves are mounted in specially formed sections of the eduction tube and the increased size of the interior of the sections is such as to prevent full sealing contact of the sealing elements of the plunger.

To extend the economic possibility of the kick-off method of gas lift requires a plunger to realize the maximum efiiciency in gas utilization and at the same time minimize the emulsion difiiculties that are found in some wells operated by gas lift. With the side pockets in the eduction tube for reception of the retrievable type of kick-oil valve, 21 long plunger serves to bridge the full length of the side opening. There can be one or more of such side pockets or openings depending on the number of kickoff valves required. In accordance with my invention, I provide a plunger having a total over-all length substantially greater than the length of any laterally expanded section of the tubing and this plunger takes the form of two sealing elements separated by a central spacer. The brush type sealing element has been found to be particularly well suited for this long form of plunger.

Other and more detailed objects and advantages will appear hereinafter.

In the drawings:

FIGURE la is a side elevation showing a well head installation employed in connection with a preferred embodiment of my invention.

FIGURE 1b forms a continuation of the lower end of FIGURE 1a.

FIGURE 2 is a side elevation partly in section showing the parts on an enlarged scale.

FIGURE 3 is a sectional detail taken substantially on the lines 3-3 as shown in FIGURE 1a.

FIGURE 4 is a side elevation partly in section showing the releasable connection between the upper and lower parts of the well head assembly.

FIGURE 5 is a sectional plan view taken substantially on the lines 55 as shown in FIGURE 2.

FIGURE 6 is a side elevation partly in section showing details of the plunger.

FIGURE 7 is a sectional view partly broken away of the device shown in FIGURE 6.

FIGURE 8 is a sectional plan view taken substantially on the lines 8-8 as shown in FIGURE 6.

FIGURE 9 is a sectional detail showing a modification.

Referring to the drawings, the free piston well purrnp device includes an eduction tube It) having its upper end fixed to a well head assembly generally designated 11 and comprising an upper part 12 and a lower part 13, joined by a separable connector 14. A plunger 15 travels vertically within the eduction tube 10 and is adapted to be received Within the upper part 12 of the well head assembly 11. Well fluid brought up through the eduction tube to the surface by means of the plunger 15 passes from the well head assembly through the discharge pipe 16.

In accordance with my invention, the plunger 15 may comprise a pair of sealing members 17 and 13 separated by a central spacer 19. This spacer may take the form of a length of conventional sucker rod joined to the sealing members by means of the coupling guides 20 and 21. Each of the sealing members 17 and 18 comprises a longitudinal mandrel 22 having a continuous helical groove 23 provided on its outer surface. A helical fin 24 thus forms the side of the groove. The retainer 25 is received within the helical groove 23 and the retainer supports the brush bristles in a generally radial direction. The brush 26 comprising the retainer and bristles is assembled on the mandrel in the manner of a nut on a bolt, and is fixed in place to prevent relative movement. Instead of mounting a helical brush retainer in a helical groove, a plurality of circular brush rings can be used, if desired.

The free outside diameter of the brush 26 when unconfined is very slightly smaller than the internal diameter of the eduction tube 10, that is to say, the tips of brush bristles define a cylinder having a diameter smaller than the internal diameter of the eduction tube. The bristles of the brush 26 are believed to develop localized turbulence when the plunger moves upward in the eduction tube, carrying a load of well fluid, and driven by gas pressure from below. The mandrel 22 carrying the brush 26 is relatively long and substantially longer than the diameter of the brush thereby providing a substantial number of convolutions of the brush for each sealing member 17 and 18.

As shown in FIGURE 8, the upper guide 27 is noncircular in cross section and has rounded portions 28 with running clearance within the inner surface 29 of the eduction tube 10. The flat surfaces 30 have substantial clearance with the surface 29 and also provide wrench contacting areas.

The guides 20, 21 and 31 have the same external configurations as the guide 27. The guide 20 is connected to the lower end of the mandrel 22 by means of threads 32 and locked by means of a set screw 50. The brush 26 is thus confined between the guides at opposite ends of the mandrel 22. The guides serve to center the brush 26 within the inner surface 29 of the eduction tube 10 when the bristles are relatively soft and formed of nonmetallic material, such as nylon.

In the modified form of my invention shown in FIG- URE 9, the guides 27a may be given greater running clearance within the interior of the eduction tube and the helical fin 24a may provide the centering function for the helical brush 26a. In other respects, the plunger 15a is substantially the same as plunger 15.

The casing 33 extends downward into the well from the well head assembly 11 and the eduction tube is positioned within this casing. Sections 34 of the eduction tube 10 may be provided which are laterally enlarged to receive retrievable kick-01f valve assemblies (not shown). Laterally positioned pockets 35 are thus provided at one or more locations along the length of the eduction tube 10. These pockets are longer than the length of either of the sealing elements 17 or 18 but the overall length of the plunger is substantially longer than these pockets 35. Accordingly, the sealing effect is not lost when the plunger 15 moves upward in the eduction tube 10 even though the pockets 35 are too large to be sealed by the sealing portions 17 and 18; while one of the sealing elements is passing through a section 34, the other sealing element on the plunger remains in sealing position within adjacent sections of the eduction tube 10. The dotted lines in FIGURE 1a show the position of the plunger 15 within the upper part 12 of the well head assembly 11. The plunger 15 is also shown in FIGURE 1b to illustrate its length compared to the length of one of the laterally enlarged sections 34. Only one plunger 15 is used however, and it is shown in two different positions on the drawing for clarity of illustration.

The lower part of the well head assembly 11 includes the casing head 36 and the master gate valve 37. A hinge 38 having a horizontal axis laterally offset from the axis of the eduction tube connects the upper and lower parts of the well head assembly 11. A union 39 connects adjacent ends of the tubular parts. Control mechanism 40 which may be of the type disclosed in the copending application of William A. Shaw, Serial No. 640,365, filed February 15, 1957, may be provided to control the cycling operations of the plunger 15. An extended stack 41 connects the control mechanism 40 to the bumper support 42. A compression spring 43 is mounted on this support and extends downward into the stack 41 and serves to cushion the deceleration of the plunger 15 at the upper end of its stroke. Guy wires 44 may be attached to the coupling 45 to hold the stack 41 in upright position.

When it is desired to remove the plunger 15 for inspection, replacement or repair, the discharge line 16 is disconnected by means of the union 46, and the guy wires 44 are released. The union 39 is disconnected and the pole 48 is used to swing the stack 41 and upper portion 12 of the well head assembly about the hinge 38 away from vertical position to a position such as that shown in FIGURE 4. The plunger 15 may then conveniently be withdrawn laterally from the upper portion 12 of the well head assembly. Prior to swinging the stack 41 and upper portion 12 of the well head assembly about the hinge 38, the screw 47 may be turned and projected into the return path of the plunger 15 to trap it within the stack 41. The screw 47 is retracted when the plunger 15 is to be withdrawn laterally from the upper portion of the well head assembly.

Having fully described my invention, it is to be understood that I do not wish to be limited to the details herein set forth but my invention is of the full scope of the appended claims.

I claim:

1. A plunger adapted to travel in the eduction tube of a free piston well pump device, comprising: a mandrel having a brush mounted on the outer surface thereof, the brush being formed of bristles extending outward and the tips of the brush bristles defining a cylinder having a smaller diameter than the internal diameter of said eduction tube, the said brush being substantially longer longitudinally along said mandrel than the said diameter defined by the bristle tips, and guides on the mandrel at opposite ends of the brush having running clearance with said inner surface of the eduction tube.

2. A plunger adapted to travel in the eduction tube of a free piston well pump device, comprising: a solid mandrel having a continuous helical groove on the outer surface thereof, a bristle brush mounted in the groove and the tips of the brush bristles defining a cylinder having a smaller diameter than the internal diameter of said eduction tube, the said brush being substantially longer longitudinally along said mandrel than the said diameter defined by the bristle tips, and non-circular guides on the mandrel at opposite ends of the bristle brush proportioned to have running clearance with said inner surface of the eduction tube.

3. A plunger adapted to travel in the eduction tube of a free piston well pump device, comprising: a mandrel having a continuous helical bristle brush mounted on the outer surface thereof and the tips of the brush bristles defining a cylinder having a smaller diameter than the internal diameter of said eduction tube, the said brush being substantially longer longitudinally along said mandrel than the said diameter defined by the bristle tips, a continuous helical fin on the mandrel adjacent the brush, the outer diameter of the fin being substantially less than the inner diameter of the eduction tube, and metallic guides on the mandrel at opposite ends of the bristle brush proportioned to have running clearance with the inner surface of the eduction tube.

4. A plunger adapted to travel in the eduction tube of a free piston well pump device, comprising: a mandrel having a continuous helical bristle brush mounted on the outer surface thereof and the tips of the brush bristles defining a cylinder having a smaller diameter than the internal diameter of said eduction tube, the said brush being substantially longer longitudinally along said mandrel than the said diameter defined by the bristle tips, and a continuous helical fin on the mandrel adjacent the bristle brush proportioned to have running clearance with the inner surface of the eduction tube.

References Cited in the file of this patent UNITED STATES PATENTS 187,341 Abrams Feb. 13, 1877 1,021,600 Heeter Mar. 26, 1912 1,130,181 Lock Mar. 2, 1915 1,189,798 Dillon July 4, 1916 1,827,842 Getty Oct, 20, 1931 1,828,124 Bower Oct. 20, 1931 2,017,434 Church Oct. 15, 1935 2,018,205 Evans Oct. 22, 1935 2,055,287 Giraud Sept. 22, 1936 2,074,213 Deem Mar. 16, 1937 2,601,691 Dyer July 1, 1952 2,604,647 Stephens July 29, 1952 2,762,308 Tomlinson Sept. 11, 1956 2,802,535 Taylor Aug. 13, 1957 2,806,429 Anderson et al. Sept. 17, 1957 2,812,717 Brown Nov. 12, 1957 

